The invention relates to hydraulic braking systems comprising a brake booster. More precisely, the invention relates to a pneumatic brake booster.
The invention applies in particular to the motor industry, and more particularly to the industry of braking systems for motor vehicles.
A hydraulic braking system for a motor vehicle of the known type comprises a brake pedal, a pneumatic brake booster, a master cylinder connected to a brake fluid reservoir, a brake fluid circuit and at least one braking member actuated by the brake fluid. The hydraulic braking system may also comprise a hydraulic block.
The brake pedal actuated by a driver is mechanically coupled to the pneumatic brake booster. The pneumatic brake booster is inserted between the brake pedal and the master cylinder. Its function is to amplify a force applied to the brake pedal and to transmit it to the master cylinder. The master cylinder supplied with brake fluid by the brake fluid reservoir pressurizes the brake fluid in the brake fluid circuit under the action of the pneumatic brake booster. The brake fluid acts on the braking member. When the braking member is of the disc brake type, the brake fluid arrives under pressure in a calliper to push a piston to a brake pad and apply a brake disc.
The hydraulic block is an ancillary device comprising a pump making it possible to inject pressurized brake fluid into the circuit. The hydraulic block may operate independently of an action on the brake pedal by the driver. For example, in wet road conditions, it may be actuated to dry the wet brake discs, which makes it possible to ensure more effective braking when the time comes. It may also act as a supplement to the braking system of the known type described above to enhance braking performance in an emergency (anti-lock braking system ABS or electronic stability programme ESP).
In addition, to determine the braking instructions of the driver, necessary in particular to the coordinated operation of the aforementioned devices, the braking system comprises a plurality of sensors. A first exemplary sensor is a sensor for the lighting of brake lights designed to switch on the brake lights of the vehicle when the brake pedal is pressed. Another exemplary sensor is a travel sensor designed to give an indication of the degree of braking demanded by the driver. When measuring, these sensors interact with moving parts, for example the brake pedal.
The motor vehicle hydraulic braking system of the known type furnished with the aforementioned sensors is complex. This complexity causes added cost to the whole system because of the number of sensors, and their installation during the manufacture of a motor vehicle. In addition, it also causes a risk to the reliability of the braking system because of the interaction of the sensors with moving parts.